The present invention relates to a method and apparatus for manufacturing three-dimensional work pieces. Flat work pieces in this context are not considered to be three-dimensional work pieces, even if they have a substantial thickness. An interior car part is a typical example of a three-dimensional work piece manufactured according to the invention.
In my copending application now U.S. Pat. No. 4,273,738, a lower mold cooperates with an upper mold for shaping an initially flat sheet of plastic material. At least one mold or support carries trimming tools which are moved through the respective mold in order to trim the work piece while it is still in the same mold. My prior application does not teach the cooperation of one or two primary molds with several secondary molds in sequence.
My U.S. Pat. No. 4,106,379 which issued on Aug. 15, 1978, for an apparatus for trimming three-dimensional work pieces discloses a lower support which cooperates with trimming tools and which may shuttle back and forth between a loading station and the trimming station.
U.S. Pat. No. 4,063,477 discloses an apparatus and method for cutting carpet. A stationary lower support and a vertically movable upper support held by pre-shaped carpet in position for the cutting operation. Vertically movable first cutting means travel through the lower and upper support which hold the carpet during the cutting. Second cutting means are positioned for cutting in directions extending at an angle to the vertical or horizontal direction. The apparatus of U.S. Pat. No. 4,063,477 is also not suitable for the sequential shaping, foaming, and trimming of the same work piece while the work piece is retained on the same primary mold during all manufacturing steps.
U.S. Pat. No. 3,273,203 discloses an apparatus for transferring plastic sheet material from one station to another station in a system of cooperating machines.
The prior art machines are not suitable for first forming a plastic sheet into a desired three-dimensional shape and then foaming and trimming the sheet or rather the three-dimensional shape.